The new generation of tachographs does not store data by recording on a paper record chart as previously but in digital form electronically in a memory. The so called digital tachograph to be introduced shortly on the market operates with an internal memory and a chip card, that is to say an external storage medium, when storing the data. The chip card is completely accommodated by the digital tachograph and is completely isolated from the environment by means of mechanical provisions during the data transmission between the internal memory of the tachograph and the memory of the chip card. This is intended to prevent manipulations. The advantage of using a chip card consists in that the latter can be completely isolated from the environment. However, the great expenditure associated with the isolation during the data transmission is disadvantageous. The data card must be accommodated completely by the digital tachograph which, accordingly, must have a device for automatically receiving and delivering. In addition, it must be possible to close the opening through which the data card enters into the tachograph securely against manipulation and relevant regulations require that this shutter is locked in the closed position. The high degree of mechanical security precautions against manipulation is associated with high costs and great complexity.